The invention relates generally to a scale testing vehicle and more specifically to a self-powered cart adapted to transport calibrated weights, the total weight of the cart and weights being utilized to calibrate platform scales.
Platform scales are well known in the art and are utilized for many purposes. For example, platform type scales are used in commercial grain operations for measuring the amount of grain brought to an elevator. Similarly, governments utilize platform scales in their vehicle weight limit enforcement programs to determine whether semi-trailer and tractor units are complying with highway load limits.
The scales may be either mechanical or electronic scales. In either event, the scales often have a plurality of individual scale platforms, for example, a series of three platforms. By mechanical linkage or by electronic load cells, as a vehicle rests on one or more of the platforms, the vehicle is indicated by the scale.
It is not unusual for platform scales to measure vehicles and their loads weighing as high as twenty tons and in some cases, as high as one hundred tons. Dirt and friction have a tendency to build up at critical points in mechanical scale mechanisms and restrict action of the pivots. Winter ice also can restrict the action of a scale platform. When this occurs, the scales read a lower weight than the actual weight. Similarly, electrical drift in the components of electronic scales affects their calibration. In this case, the reading may be either above or below the proper weight. In either event, the consequences of inaccurate weight indication such as overpayment or underpayment for a load of grain or detention of a legally loaded vehicle are manifest.
Accordingly, the prior art has recognized for a long time that it is important to periodically calibrate platform scales. It also is known that the calibration accuracy of a scale will vary at different loadings. Therefore, calibration techniques established by state agencies often require platform scales to be calibrated at different loadings; the heaviest loading often double the scales' rate capacity.
In the past, platform scales were tested by placing different numbers of individual weight units, normally either five hundred pound units or one thousand pound units, upon the individual platform sections of a platform scale. It was not unusual to have two men spend a considerable amount of time unloading the weights from a vehicle which carried them to a scale site, testing the scale and reloading the weights back onto the vehicle.
One prior art solution involves a vehicle capable of concentrating its entire calibrated load on one section of a multi-section scale. The vehicle further includes a hydraulic crane which loads and unloads calibrated thousand pound weights from the vehicle onto a section of the scale, or onto a cart which is manually moved onto a a section of the scale, which requires individual testing or calibration at a lesser load. Even with this vehicle or prior art method, it has been laborious and time consuming to transport and position the calibrated weight on the scale section under test.